The pre-World War I works of Schoenberg, Berg, and Webern, "give a glimpse of a new universe of emancipated discourse, unfortunately quickly abandoned when Schoenberg returned to the classical musical shapes upon adopting the twelve-tone system."
Notes from Wikiquote
Cited in Albright, Daniel (2004). Modernism and Music: An Anthology of Sources. University of Chicago Press. ISBN 0226012670.